1. Field of the Invention
This invention relates to the nondestructive evaluation of a wooden member accessible from a single end, and having particular utility for evaluating wooden members having one end embedded in the soil, fresh or marine water, or the like, or otherwise inaccessible. It also has particular utility for test methods for monitoring biological or chemical degradation of wood products.
2. Background Art
Wooden members find a variety of applications in pilings for foundations, utility poles, and supports for guard rails. In these applications a portion of the wooden member is embedded in the soil to provide support for loads directed against the free end. Such wooden members provide an inexpensive but sturdy construction solution. For example, wooden pilings may carry 15 to 20 tons per piling.
Despite their strength and low costs, wooden members are subject to weakening from decay, insect infestation, and chemical attack. White and brown rot fungi may attack wood in contact with the soil, soft rot fungi and bacteria may attack woods maintained in even a low oxygen environment such as when submerged in fresh water. Wooden members embedded in the soil may also be attacked by subterranean termites, wood boring beetles, carpenter ants, and carpenter bees. Marine borers may attack wood used in marine waters. Chemicals, including those used to protect wood from biological attack or fire, may also weaken wooden members.
The destructive mechanisms of decay, and insect and chemical attack frequently cause internal damage or a weakening of the wood on a microscopic level not visible to the eye. Further, much of the damage may occur out of sight. For this reason, in most applications, it is critical that wooden members in contact with the soil or other medium, be inspected periodically to insure their integrity.
A variety of non-destructive tests are available to evaluate the integrity of a wooden member that is free from surrounding soil, water, other medium, or contact with other members. However, it is not practical to extract the wooden members for testing because of the disproportionate cost of such removal and reinsertion. Typically such wooden members are providing ongoing support for a structure, further complicating their removal.
Current testing procedures for wooden members in situ, that is embedded in the soil or other medium, are difficult and ineffective. Sample borings may be taken into the wooden member to evaluate its internal state if the area of possible damage may be localized. Alternatively, non-destructive x-ray and acoustic techniques may be employed to examine the internal structure of the wooden member. These latter techniques are effective only above the soil line, or a very small amount below the soil line, because of interference from the physical presence of the soil in which the wooden member is embedded and because both sides of the wooden member must be accessible.